Atherosclerosis, the clogging of arteries, is a leading cause of coronary heart disease. Blood flow through the peripheral arteries (e.g., carotid, femoral, renal etc.), is similarly affected by the development of atherosclerotic blockages. One conventional method of removing or reducing blockages in blood vessels is known as rotational atherectomy. A long guidewire is advanced into the diseased blood vessel and across the stenotic lesion. A hollow drive shaft formed from a torque transmitting coiled wire(s) is advanced over the guidewire. The distal end of the drive shaft terminates in a burr provided with an abrasive surface formed from diamond grit or diamond particles. The burr is positioned against the occlusion and the drive shaft rotated at extremely high speeds (e.g., 20,000-160,000 rpm).
As the burr rotates, the physician slowly advances it so that the abrasive surface of the burr scrapes against the occluding tissue and disintegrates it, reducing the occlusion and improving the blood flow through the vessel. Such a method and a device for performing the method are described in, for example, U.S. Pat. No. 4,990,134 to Auth. It is also known from U.S. Pat. No. 6,132,444 to Shturman (the instant inventor) et al., to provide a drive shaft which is also formed from a single layer of torque transmitting coiled wire or wires but different to the device described in U.S. Pat. No. 4,990,134 to Auth, mentioned above, by providing the drive shaft with an eccentric enlarged diameter section located proximally to and spaced away from the distal end of the drive shaft. This drive shaft is formed from a single layer of torque transmitting coiled wire(s). According to U.S. Pat. No. 6,132,444 to Shturman, abrasive particles are located around a maximum diameter of the eccentric segment of the drive shaft thereby forming an eccentric abrasive element positioned proximally to and spaced away from the distal end of the drive shaft.
A rotational atherectomy device with distal embolic protection capability is known from WO 2006/126076 to Shturman (the current inventor). In one preferred embodiment of this known Shturman application the distal end of the fluid impermeable drive shaft is advanced across the stenotic lesion to be treated and flushing fluid is pumped through the drive shaft in an antegrade direction to enter the vessel through at least one luminal opening located distally to the abrasive element. As a result of a continued flow of flushing fluid into the vessel in this way, a fluid pressure is generated in the vessel distal to the abrasive element which is sufficient to generate a retrograde flow of at least a portion of the flushing fluid around the abrasive element and the fluid impermeable drive shaft. This retrograde flowing flushing fluid entrains stenotic debris abraded by the rotating abrasive element and flows into a lumen of stationary drive shaft sheath thereby preventing distal migration of debris along the treated vessel. In the most preferred embodiment, abraded debris are not only being removed from the treated vessel but from the patient altogether.
According to the preferred embodiments of WO 2006/126076, it is also possible to provide inflatable support elements located distal and proximal to the abrasive element. The inflatable support elements may have centers of mass which are offset from the longitudinal axis of the drive shaft. Such support elements act as counterweights to the eccentric abrasive element, i.e. an abrasive element that has its centre of mass offset from the longitudinal axis of the drive shaft. Alternatively, the abrasive element and the support elements may have centers of mass which lie along the longitudinal axis of the drive shaft.
The rotational atherectomy device with fluid inflatable support elements has a smaller crossing profile than the rotational atherectomy device with solid support elements. The term ‘crossing profile’ refers to a maximum cross-sectional dimension of that portion of the device which has to be advanced across the stenotic lesion. All embodiments of the device described in WO 2006/126076 have to be advanced along the treated vessel and across the stenotic lesion over the guidewire. The devices with fluid inflatable support elements known from WO 2006/126076 allow to reduce the crossing profile of the drive shaft of the device but they still have to be advanced across the stenotic lesion over the guidewire. The outer diameter of the drive shaft of any rotational atherectomy device with distal protection which is advanced over a guidewire may still be too large to cross very tight stenotic lesions. The present invention therefore seeks to provide a rotational atherectomy device with distal protection capability which does not require use of a guidewire for its advancement across the stenotic lesion to be treated. Such device may have a crossing diameter which is smaller than the crossing diameter of known rotational atherectomy devices with distal protection capability. The present invention also seeks to provide a rotational atherectomy device with distal protection capability that does not require occlusion of a distal end of the guidewire lumen prior to initiating flow of pressurized fluid through the guidewire lumen.